1. Field of the Invention
The present invention is directed to computer systems; and more particularly, it is directed to the processing of digital images using computer systems.
2. Description of the Related Art
Digital image editing is the process of creating and/or modifying digital images using a computer system. Using specialized software programs, users may manipulate and transform images in a variety of ways. These digital image editors may include programs of differing complexity such as limited-purpose programs associated with acquisition devices (e.g., digital cameras and scanners with bundled or built-in programs for managing brightness and contrast); limited editors suitable for relatively simple operations such as rotating and cropping images; and professional-grade programs with large and complex feature sets.
Digital images may include raster graphics, vector graphics, or a combination thereof. Raster graphics data (also referred to herein as bitmaps) may be stored and manipulated as a grid of individual picture elements called pixels. A bitmap may be characterized by its width and height in pixels and also by the number of bits per pixel. Commonly, a color bitmap defined in the RGB (red, green blue) color space may comprise between one and eight bits per pixel for each of the red, green, and blue channels. An alpha channel may be used to store additional data such as per-pixel transparency values. Vector graphics data may be stored and manipulated as one or more geometric objects built with geometric primitives. The geometric primitives (e.g., points, lines, paths, polygons, Bézier curves, and text characters) may be based upon mathematical equations to represent parts of vector graphics data in digital images. The geometric objects may typically be located in two-dimensional or three-dimensional space. A three-dimensional object may be represented in two-dimensional space for the purposes of displaying or editing the object.
Digital images such as photography, paintings, and moving pictures may include objects affected by one or more light sources. The light sources may affect the visual imagery of objects in an image even though the light sources are absent in the image itself. For example, a light bulb located beside a photographer may affect the visual imagery of the objects in an image obtained by the photographer. In computer vision and graphics, estimation of the lighting environment of an image may be desirable for many applications. For example, determining the location and relative intensity of one or more light sources may be useful in recreating the lighting environment to obtain a second image or to ensure a consistent lighting environment when re-shooting a motion picture scene.